For most words, if you are referring to more than one you simply add an s to the word.

The cat was playing = one cat.

The cats were playing = more than one cat.

However, adding an apostrophe in a simple sentence like this can create confusion as it signifies ownership. So you need to use it correctly to make sure it’s interpreted correctly. For instance, if you were to write:

The cat’s were playing.

Then that would be wrong. That apostrophe is not needed. Not unless you are referencing something belonging to the cat. Including it in the sentence above invites the question “the cat’s what were playing?” Does the cat have its own menagerie of miniature mouseketeers who like to re-enact scenes from the Spanish Inquisition? (Please say yes, I’d pay to see that!)

If that were the case, the sentence should actually be:

The cat’s mouseketeers were playing.

That shows the cat has ownership of the mouseketeers. But what if several cats all own bands of miniature mouseketeers?

Then cat becomes cats, as it’s pluralised, but we need to add an apostrophe to show all those cats have ownership of bands of mouseketeers. And this is where things can get a tad confusing. By rights, the sentence would become:

The cats’s mouseketeers were playing.

But that’s kinda awkward to say isn’t it? It reads as though you’d pronounce it ‘catsis’. So because of that tricky s’s, a new rule is introduced. Just add an apostrophe after the s. Which gives you:

The cats’ mouseketeers were playing.

Because simply adding an apostrophe after a noun that is already made plural by an s indicates possession. Possession of the many. Possession by all the cats. (And no, I don’t mean they’ve all been dabbling in the dark arts. Honestly, behave will you! Not that kind of possession!!)

To recap:

The word cats is plural (meaning more than one cat).

Adding an apostrophe to a plural noun (after the s) indicates possession.

Therefore “The cats’ mouseketeers were playing” is a sentence that tells us several cats have got little mouseketeers, and all those mouseketeers belonging to all those cats were playing. We don’t know exactly what they were playing because we haven’t actually been told. It could be miniature trombones, or games of hide and seek, but to keep yours truly happy we’re going to presume what they’re doing is re-enacting scenes from the Spanish Inquisition. After all, nobody expects the Spanish Inquisition.

Most words ending in s or ss are pluralised by adding an es on the end, making bosses, crosses, cactuses, octopuses and businesses. But then there’s cacti too. Also an acceptable pluralisation of cactus. And octopi. Which although widely used, is not an acceptable pluralisation of octopus. “Oh my god, how is anyone supposed to know this?” You might well ask. And I don’t rightly know the answer to that. Trial and error? Continued learning? English is hard, we all know that. We all have hiccups. But don’t worry, you’re allowed to make mistakes. You’re allowed to change your mind. God knows I’ve used octopi in the past when talking about more than one octopus. But now I use octopuses. And that’s ok.

Personally, I prefer cactuses as well now, just because it fits in better with ‘the rules’. But cacti is fine. It might even be a better choice if, for example, you’re writing about horticulture, where Latin words are expected. Because it all comes down to etymology in the end. Cacti comes from the Latin, where you add an i, but octopus is from the Greek, where you don’t. So cacti is allowed, but octopi isn’t. Still, we can safely say the majority of words ending in an s are made plural by adding es.

English eh? Always so full of knotty problems.

So what if you want to show possession of a word that ends in s already? Well, the rules are pretty much the same as before. All you need to do is get your head round all those s’s. (Incidentally, it is ok to use an apostrophe if you’re writing the plural of single letters like s’s. Otherwise you’d just be writing ss, which doesn’t make sense to anyone.)

If we want to talk about a boss who has a new tie, it’s:

The boss’s new tie.

If there’s a whole gang of bosses, all with matching new ties (perhaps they got a bulk discount at Fancy Man Clothing?) then it’s:

The bosses’ new ties.

As you would expect there are certain exceptions to the rule of adding es. It is English after all! For instance oasis doesn’t add the es on the end to pluralise. Oasis knocks off the ‘is’ first and becomes oases when discussing more than one. But apart from that the same rules apply. Talking about a whole stack of oases in the desert would simply be:

The desert was filled with many oases.

If you wanted to specify a further detail belonging to those oases, you could use the apostrophe after s rule again, for instance:

The oases’ colours were very beautiful.

That punctuation would clarify that you were talking about the colours of more than one oasis. The colours “belonging to” those oases.

Other words, such as those ending in ch and ex follow similar rules to those already discussed here i.e. torch becomes torches, and hex becomes hexes. Proper nouns (that’s proper names like Sarah, David, London, the Guardian, Mr Barker, the Rolling Stones) are also treated in a similar fashion when it comes to adding apostrophe-s to show ownership. The main difference is that style guide rules often diverge over best practice when it comes to proper nouns. So it’s best to check what they want first. There’s also the tricky business of names that end in s, but that really deserves a whole article of its own. And it just so happens I’ve got one right here! You lucky people. Go wild in the aisles for the ‘Names That End in S’ feature article. Yay!

Please bookmark this page and check back as I’ll be linking the new ‘Names That End in S’ feature article here in two shakes of a lamb’s tail.